Derivatives (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010	Sep. 30, 2011		Sep. 30, 2010	Dec. 31, 2010
Derivative [Line Items]
Fixed price for the outstanding extendible oil swaps of daily production per Bbl	$ 100.00			$ 100.00
Premiums paid for put options on oil and natural gas commodity derivative contracts	33,000,000
Volumes of natural gas production on settled derivatives	16,140			48,317
Average contract price per MMBtu on settled derivatives	8.24			8.24
Volumes of oil production on settled derivatives	2,123			5,794
Average contract price per barrel on settled derivatives	87.10			85.19
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	980,187,000			980,187,000			637,836,000
Derivative Liability, Fair Value	210,654,000			210,654,000			398,902,000
Realized gains (losses): [Abstract]
Commodity derivatives [Member]	65,036,000		82,910,000	162,926,000		228,573,000
Interest rate swaps	0		0	0		(8,021,000)
Canceled derivatives	26,752,000		(49,590,000)	26,752,000		(123,865,000)
Total realized gains (losses)	91,788,000		33,320,000	189,678,000		96,687,000
Unrealized gains (losses): [Abstract]
Commodity derivatives	732,452,000		(39,405,000)	470,601,000		34,726,000
Interest rate swaps	0		38,089,000	0		63,978,000
Total unrealized gains (losses)	732,452,000		(1,316,000)	470,601,000		98,704,000
Total gains (losses): [Abstract]
Gains on oil and natural gas derivatives	824,240,000		43,505,000	660,279,000		263,299,000
Gains (losses) on interest rate swaps	0		(11,501,000)	0		(67,908,000)
Total gains (losses) on derivative instruments	824,240,000		32,004,000	660,279,000		195,391,000
Amount of realized gain (loss) from cancelation before the settlement date of commodity derivative contracts.	27,000,000
Amount of realized gain (loss) from cancelation before the settlement date of interest rate derivatives.			(50,000,000)			(124,000,000)
Natural Gas Derivative Instruments [Member] | Fixed price swaps [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	7,975			7,975
Weighted Average Fixed Price	9.50			9.50
Natural Gas Derivative Instruments [Member] | Puts [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	4,850			4,850
Weighted Average Short Put Price	5.97			5.97
Natural Gas Derivative Instruments [Member] | PEPL puts [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	3,315	[1]		3,315	[1]
Weighted Average Short Put Price	8.50	[1]		8.50	[1]
Natural Gas Derivative Instruments [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	16,140			16,140
Weighted Average Fixed Price	8.24			8.24
Oil Derivative Instruments [Member] | Fixed price swaps [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	1,466	[2]		1,466	[2]
Weighted Average Fixed Price	91.82	[2]		91.82	[2]
Oil Derivative Instruments [Member] | Puts [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	588			588
Weighted Average Short Put Price	75.00			75.00
Oil Derivative Instruments [Member] | Collars [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	69			69
Weighted Average Floor Price	90.00			90.00
Weighted Average Ceiling Price	112.25			112.25
Oil Derivative Instruments [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	2,123			2,123
Weighted Average Fixed Price	87.10			87.10
Natural Gas Basis Differential Positions [Member] | PEPL basis swaps [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	8,885	[1]		8,885	[1]
Weighted Average PEPL basis swaps hedged differential	(0.96)	[1]		(0.96)	[1]
Oil Timing Differential Positions [Member] | Trade month roll swaps [Member] | 2011 [Member]
Derivative [Line Items]
Annual Hedged Volume	1,380	[3]		1,380	[3]
Weighted Average Trade Month Roll Swaps Hedged Differential	0.22	[3]		0.22	[3]
Natural Gas Derivative Instruments [Member] | Fixed price swaps [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	49,410			49,410
Weighted Average Fixed Price	6.10			6.10
Natural Gas Derivative Instruments [Member] | Puts [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	25,364			25,364
Weighted Average Short Put Price	6.25			6.25
Natural Gas Derivative Instruments [Member] | PEPL puts [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	0	[1]		0	[1]
Weighted Average Short Put Price	0	[1]		0	[1]
Natural Gas Derivative Instruments [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	74,774			74,774
Weighted Average Fixed Price	6.15			6.15
Oil Derivative Instruments [Member] | Fixed price swaps [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	7,741	[2]		7,741	[2]
Weighted Average Fixed Price	97.34	[2]		97.34	[2]
Oil Derivative Instruments [Member] | Puts [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	2,196			2,196
Weighted Average Short Put Price	90.00			90.00
Oil Derivative Instruments [Member] | Collars [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	0			0
Weighted Average Floor Price	0			0
Weighted Average Ceiling Price	0			0
Oil Derivative Instruments [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	9,937			9,937
Weighted Average Fixed Price	95.72			95.72
Natural Gas Basis Differential Positions [Member] | PEPL basis swaps [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	37,735	[1]		37,735	[1]
Weighted Average PEPL basis swaps hedged differential	(0.89)	[1]		(0.89)	[1]
Oil Timing Differential Positions [Member] | Trade month roll swaps [Member] | 2012 [Member]
Derivative [Line Items]
Annual Hedged Volume	5,490	[3]		5,490	[3]
Weighted Average Trade Month Roll Swaps Hedged Differential	0.22	[3]		0.22	[3]
Natural Gas Derivative Instruments [Member] | Fixed price swaps [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	57,067			57,067
Weighted Average Fixed Price	5.88			5.88
Natural Gas Derivative Instruments [Member] | Puts [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	25,295			25,295
Weighted Average Short Put Price	6.25			6.25
Natural Gas Derivative Instruments [Member] | PEPL puts [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	0	[1]		0	[1]
Weighted Average Short Put Price	0	[1]		0	[1]
Natural Gas Derivative Instruments [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	82,362			82,362
Weighted Average Fixed Price	6.00			6.00
Oil Derivative Instruments [Member] | Fixed price swaps [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	8,413	[2]		8,413	[2]
Weighted Average Fixed Price	98.27	[2]		98.27	[2]
Oil Derivative Instruments [Member] | Puts [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	2,190			2,190
Weighted Average Short Put Price	90.00			90.00
Oil Derivative Instruments [Member] | Collars [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	0			0
Weighted Average Floor Price	0			0
Weighted Average Ceiling Price	0			0
Oil Derivative Instruments [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	10,603			10,603
Weighted Average Fixed Price	96.56			96.56
Natural Gas Basis Differential Positions [Member] | PEPL basis swaps [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	38,854	[1]		38,854	[1]
Weighted Average PEPL basis swaps hedged differential	(0.89)	[1]		(0.89)	[1]
Oil Timing Differential Positions [Member] | Trade month roll swaps [Member] | 2013 [Member]
Derivative [Line Items]
Annual Hedged Volume	5,475	[3]		5,475	[3]
Weighted Average Trade Month Roll Swaps Hedged Differential	0.22	[3]		0.22	[3]
Natural Gas Derivative Instruments [Member] | Fixed price swaps [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	66,156			66,156
Weighted Average Fixed Price	5.86			5.86
Natural Gas Derivative Instruments [Member] | Puts [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	23,178			23,178
Weighted Average Short Put Price	5.00			5.00
Natural Gas Derivative Instruments [Member] | PEPL puts [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	0	[1]		0	[1]
Weighted Average Short Put Price	0	[1]		0	[1]
Natural Gas Derivative Instruments [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	89,334			89,334
Weighted Average Fixed Price	5.64			5.64
Oil Derivative Instruments [Member] | Fixed price swaps [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	9,034	[2]		9,034	[2]
Weighted Average Fixed Price	95.39	[2]		95.39	[2]
Oil Derivative Instruments [Member] | Puts [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	0			0
Weighted Average Short Put Price	0			0
Oil Derivative Instruments [Member] | Collars [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	0			0
Weighted Average Floor Price	0			0
Weighted Average Ceiling Price	0			0
Oil Derivative Instruments [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	9,034			9,034
Weighted Average Fixed Price	95.39			95.39
Natural Gas Basis Differential Positions [Member] | PEPL basis swaps [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	42,194	[1]		42,194	[1]
Weighted Average PEPL basis swaps hedged differential	(0.39)	[1]		(0.39)	[1]
Oil Timing Differential Positions [Member] | Trade month roll swaps [Member] | 2014 [Member]
Derivative [Line Items]
Annual Hedged Volume	5,475	[3]		5,475	[3]
Weighted Average Trade Month Roll Swaps Hedged Differential	0.22	[3]		0.22	[3]
Natural Gas Derivative Instruments [Member] | Fixed price swaps [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	75,190			75,190
Weighted Average Fixed Price	5.90			5.90
Natural Gas Derivative Instruments [Member] | Puts [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	23,178			23,178
Weighted Average Short Put Price	5.00			5.00
Natural Gas Derivative Instruments [Member] | PEPL puts [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	0	[1]		0	[1]
Weighted Average Short Put Price	0	[1]		0	[1]
Natural Gas Derivative Instruments [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	98,368			98,368
Weighted Average Fixed Price	5.69			5.69
Oil Derivative Instruments [Member] | Fixed price swaps [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	9,581	[2]		9,581	[2]
Weighted Average Fixed Price	98.25	[2]		98.25	[2]
Oil Derivative Instruments [Member] | Puts [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	0			0
Weighted Average Short Put Price	0			0
Oil Derivative Instruments [Member] | Collars [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	0			0
Weighted Average Floor Price	0			0
Weighted Average Ceiling Price	0			0
Oil Derivative Instruments [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	9,581			9,581
Weighted Average Fixed Price	98.25			98.25
Natural Gas Basis Differential Positions [Member] | PEPL basis swaps [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	42,194	[1]		42,194	[1]
Weighted Average PEPL basis swaps hedged differential	(0.39)	[1]		(0.39)	[1]
Oil Timing Differential Positions [Member] | Trade month roll swaps [Member] | 2015 [Member]
Derivative [Line Items]
Annual Hedged Volume	0	[3]		0	[3]
Weighted Average Trade Month Roll Swaps Hedged Differential	$ 0	[3]		$ 0	[3]
Oil Derivative Instruments [Member] | Year 2016 [Member]
Derivative [Line Items]
Amount of outstanding extendible fixed price oil swaps of daily production	14,750			14,750
Oil Derivative Instruments [Member] | Year 2017 [Member]
Derivative [Line Items]
Amount of outstanding extendible fixed price oil swaps of daily production	14,750			14,750
Oil Derivative Instruments [Member] | Year 2018 [Member]
Derivative [Line Items]
Amount of outstanding extendible fixed price oil swaps of daily production	14,750			14,750

[1] Settle on the Panhandle Eastern Pipeline ("PEPL") spot price of natural gas to hedge basis differential associated with natural gas production in the Mid-Continent Deep and Mid-Continent Shallow regions.

[2] As presented in the table above, the Company has certain outstanding fixed price oil swaps on 14,750 Bbls of daily production which may be extended annually at a price of $100.00 per Bbl for each of the years ending December 31, 2016, December 31, 2017, and December 31, 2018, if the counterparties determine that the strike prices are in-the-money on a designated date in each respective preceding year. The extension for each year is exercisable without respect to the other years.

[3] The Company hedges the timing risk associated with the sales price of oil in the Mid-Continent Deep, Mid-Continent Shallow and Permian Basin regions. In these regions, the Company generally sells oil for the delivery month at a sales price based on the average NYMEX price of light oil during that month, plus an adjustment calculated as a spread between the weighted average prices of the delivery month, the next month and the following month during the period when the delivery month is prompt (the "trade month roll").